The present invention relates to the technical filed of an image reading apparatus for photoelectrically reading an image, and the like recorded on a film, and more particularly to an image reading apparatus capable of accurately detecting an image defect caused by a foreign particle deposited on a film and by a flaw of the film.
Most of the images recorded on photographic films such as negatives and reversals (which are hereinafter referred to as “films”) are conventionally printed onto light-sensitive materials (photographic papers) by a technique generally called “direct exposure” in which the image on a film is projected onto the light-sensitive material for exposure.
In contrast, recently, an image recorded on a film is read photoelectronically and is converted into digital signals, which are subjected to various kinds of image processing to produce recording image data; and a light-sensitive material is exposed with recording light modulated according to the image data, thereby the light-sensitive material is output as a print on which the image is recorded, and further the image data is also output to various recording mediums such as a CD-R and a hard disk (HD) as an image file.
According to this digital processing, since an image recorded on a film is read and subjected to image processing as digital image data, color and density can be very preferably corrected. In addition to the above, an image of high quality can be obtained by performing image processing such as gradation correction, sharpness processing (sharpness correction), and the like which is basically impossible in a printer employing ordinary direct exposure.
Incidentally, there is an image defect in an image output from a film acting as an original as a serious factor for deteriorating the quality of the image. The image defect is caused by a foreign particle such as dust, dirt, and so on deposited on the film, a flaw, scratch of the film formed by friction, and the like (hereinafter, the image defect is generally referred to as “dust/flaw”).
Conventional printers employing the direct exposure output a print whose dust/flaw is corrected in such a manner that an operator manually cleans a film or corrects the image (film) with a color material. Whereas, in the digital processing in which an image recorded on a film is read photoelectrically and processed as digital image data, it is possible to detect a dust/flaw by analyzing the image data obtained by reading the image and to correct it by executing image processing.
In digital printers, there is conventional known a method of detecting a dust/flaw of a film by reading an image of the film in an invisible region of infrared light (IR light), and the like, as a method of detecting the dust/flaw of the film (refer to JP 6-28468 A, JP 11-75039A, etc.).
That is, since IR light is not absorbed by an image (dye) recorded on a film and is scattered by a dust/flaw, it is possible to detect a dust/flaw from a change of signal intensity when the film is read with the IR light.
However, there is a case in which an image is absorbed by invisible light depending upon a type of a film and a state of an image and further depending upon a wavelength of the invisible light. At this time, even a proper portion that is not a dust/flaw is determined also as a dust/flaw and erroneously detected.
Thus, when an image is corrected according to a result of detection of a dust/flaw detected by IR light, and the like, even a proper portion of the image that is not a dust/flaw may be corrected, which deteriorates image quality conversely. Further, since a proper portion that need not be intrinsically corrected is also processed, a problem arises in that processing is time-consuming and productivity (a processing efficiency) is deteriorated.
To prevent this disadvantage, invisible light must have a wavelength that does not absorb dye at all, from which a problem is also arisen in that the design of an optical system is very difficult regarding aberration, and the like, and further a cost is greatly increased.